The following procedure ordinarily is adopted when attempting to sample a serum specimen in a blood test:
First, blood is collected from a vein using a blood-collecting tube 80 (sealed by a rubber stopper 81), of the kind shown in FIG. 7, the interior of which is depressurized with respect to the atmosphere. Thereafter, the blood is subjected to centrifugal separation when it coagulates sufficiently.
In order to extract a specimen solely from the serum layer obtained by separation, decantation or a sampling method using a pipette are available.
Decantation refers to a method in which the rubber stopper is removed and only the serum from the upper layer is poured into a separate tube by hand. This state is illustrated in FIG. 8(a).
In the method using a pipette, a pipette is inserted into the blood-collecting tube 80 via the opening from which the rubber stopper has been removed, and only the serum is sampled by the pipette. This state is shown in FIG. 8(b). Apparatus for performing these operations automatically are also available.
In any case, it is necessary to remove the rubber stopper when sampling serum. When attempting to sample serum, therefore, some of the blood naturally spills out, and there is the danger that impurities will pierce the interior of the blood-collecting tube from the outside. Thus, major problems remain.
In particular, when separated serum is divided several times for testing, sampling must be performed by repeating these sampling methods several times. This increases the possibility that the aforementioned difficulties will be encountered.